Sharpening MMM Blades

Tdog · Mar 19, 2005

I took my MMM off for the 1st time [with difficulty] a couple of months ago - - I finally got around to tilting it up on edge & chaining it to a wall. It's awfully tempting to use an angle grinder to sharpen the blades while they are still on the mower. Has anyone done this? Or is it recommended that they be removed to be shapened?

thanks,

Jack

aquetrac · Mar 19, 2005

You already have done all the hard work by taking the deck off. Remove the blades and sharpen them properly, its not a job you want to do again soon!

Tom_H · Mar 19, 2005

In checking your profile, I see that you have a BX22. The first time I took off and reattached the MMM on my BX2200, it took over half an hour for each. I now can do it in less than five minutes. There is a learning curve for the person while the parts seem to slide more smoothly following the friction and wear which come with repeated movements.

Small sized Super-Dollies can make rolling the deck easier. To lift the deck, I have an electric hoist mounted in the garage trusses. Storage can be made easier with the use of Mower-Axle storage wheels. I personally remove the blades by using an oversized wrench, which greatly increases the torque, while blocking blade movement with wooden blocks. Use of an oversized wrench makes an otherwise difficult task become easy.

Professionals will place the blades on a jig and use a bench grinder. This results in a precision edge with a constant angle. I place the blades in a bench vise and sharpen freehand with an angle grinder. There is a learning curve to this as well. I am not able to get the perfectly consistent angle one can get with a jig, however I can get a very sharp edge. I sharpen once per year, at the beginning of the cutting season.

When blades are sharpened, metal is obviously removed. It is necessary to reduce the mass on each side of the blade by an approximately equal amount. Otherwise the blade will be out of balance and the centrifugal force during high speed revolution will cause excessive vibration throughout the MMM, its support mechanisms, and the tractor. In order to insure that the blades are balanced, it is necessary to remove them. While balancing is necessary, it is not, however, rocket science. Simply hold the blade by inserting a pencil through the center hole and observe whether one side drops lower than the other. If so, grind away small amounts of metal from the heavier side until the blade balances. An even better method is to place a narrow diameter finish nail into a stud of the garage wall. This will provide a narrower and more accurate pivot point than a pencil.

Good luck!

NY_Yankees_Fan · Mar 19, 2005

( Professionals will place the blades on a jig and use a bench grinder)

Any of our machine shop folks come up with this product yet?? If so, where can I buy one. /forums/images/graemlins/grin.gif I am sure with all the BX owners here you would sell a bunch. /forums/images/graemlins/wink.gif

Mith · Mar 19, 2005

Take the blades off the mower, the time you will save not taking them off will be less than the extra time and irritation of trying to do them while theyre on.
At work we use a bench grinder and slide the blade back and forth across the stone. Personally i prefer using the grinder and the vice, its far easier and faster in my opinion.
You should take you baldes off atleast once a year so the bolts that hold them on dont become rusted or corroded in place. Every time you remove them replace them with a spot of greas on the bolt. You will thank yourself if you need new blades as they will come off as easily as you like /forums/images/graemlins/laugh.gif
Balancing is a big deal, you may find the best way is to get a bolt the size of the hole in the balde and balance it on that, but pretty much any wethod works. You may feel that a balancing tool is worth the cash, probably about $5 in the US
When you are sharpening try to move the grinder over the blade or blade over bench grinder and not just hold it in one place. this will give you a smoother cut and will prevent the balde heating up so much its properties are changed. If you can tell try to keep the pitch of the blade similar to that that it was origionally.

Tollster · Mar 19, 2005

I think you can touch them up on the deck with a file, but save the grinding for the bench. As you are more likely to meet the angle and less likely to overheat the blade. If you keep it on the deck, it'll lead to rework and increase metal removal, leading to replacing them sooner than if you did it on the benchgrinder.

rswyan · Mar 19, 2005

Delta makes a Wet/Dry Sharpening Center which I bought. They dry side (white stone) on this sharpener works pretty to sharpen a mower blade - flat grind (not hollow ground) It comes with one tool holder (a little small) and you can also pick another which is designed for sharpening planer knives (much bigger)

I have the steel to do the jig for the blades on my 72" MMM .... just haven't got around to doing it ....... probably because the grass hasn't really started to grow yet. /forums/images/graemlins/grin.gif

Tdog · Mar 19, 2005

OK all. You shamed me into taking off the blades & hitting them a lick with the angle grinder. I don't have a bench grinder yet - - soon, maybe.
I don't have a wrench large enough for the nuts. Does anyone know what size those nuts are? Whatever, I need to appologize for the pipe wrench I used. And I had to use a cheater pipe to break them loose. Dang, they were tight.
I decided not to purchase the wheel kit for storing the deck upright. I've made dollies for my box blade, tiller, & bh, but decided one was not needed for the MMM. With the deck chained against a wall, it does not take up much space. I don't need to move it around once it is upright. I used the FEL to raise it up most of the way, so my back survived the ordeal.
Now, sometime in the next few days you will see a post about how much trouble I had re-installing the MMM. Wish me luck.

B2400 · Mar 20, 2005

I've found that the flap disc for my 4.5" angle grinder works better than the regular disc for this. The flap disc looks like it has heavy sandpaper pieces layered all the way around it. It doesn't cut quite as fast but it leaves a nice smooth finish and doesn't seem to overheat the edge as easily. Yes, this is all performed with the blade in the bench vice.

Tom_H · Mar 20, 2005

As was mentioned above, grease the bolts before reinserting. Also, you should not need to torque them back as tightly as you found them. They are designed to tighten with vibration rather than loosen. I imagine they are factory installed with a very powerful impact gun-wrench. Like with an oil filter, after you do this a couple of times, you will learn the feel of how much torque will hold well without requiring excessive force to remove later.

Junkman · Mar 20, 2005

While you have the blades off, grease the spindles and observe until you see fresh grease coming out the bottom of the housings. I learned that they were not completely filled with grease before leaving the factory and after posting about this on TBN, others have found the same problem.

kubotabilly · Mar 20, 2005

Tom,
I bought my Foley-belsaw blade sharpner quite a few years ago so it looks alittle different that the new models, but it works great. I mow 6-7 acres a week, so I sharpen my blades about 5 times a season. Plus I do custom sharpening for anyone who drops their blades off at the shop. I sharpen blade sizes from my push mower to my 7 ft. woods finish mower. The sharpeners are alittle pricey /forums/images/graemlins/shocked.gif, but well worth it. Here's a link.
http://www.saw-toolsharpening.com/lawnmowerSharpening01.html

Bill

NY_Yankees_Fan · Mar 21, 2005

( The sharpeners are alittle pricey )

MODEL 440 ROTARY MOWER BLADE GRINDER
$499.00 $469.00 On Sale

Looks great but I think CFO would turn down this request. /forums/images/graemlins/grin.gif

Someone got to have a jig they use with a grinder /forums/images/graemlins/confused.gif

Larry (Moweraxle) are you reading this? Looks like another product to go with your family of MMM products. I see package deal possibilities here /forums/images/graemlins/cool.gif /forums/images/graemlins/grin.gif

gsganzer · Mar 21, 2005

As someone else mentioned. You've already done the hard work by getting the mower off and tilted up. I'd remove the blades to sharpen them. This allows you to check them for balance and swap them around. Blade 1 goes to 2, 2 to 3, 3 to 1. Also, while you have the blades off, pull the bottom spindle dust cups and check for grease.

Tdog · Mar 21, 2005

Sorry for the ignorance here, but this is the 1st time I've had the bottom of the deck exposed. While I had the blades off, I pulled off the cap [dust cap?]. There was a little grease inside each cap. Should there have been more? I greased all the fittings when I 1st removed the deck back in December. Gotta say, I found some zerks that I did not know existed.

kubotabilly · Mar 21, 2005

Tdog,
There should be just alittle grease in the dust cap. Try not to over grease the spindles or you'll have it coming out the top of the spindles and slinging it all over the belt. Every time I sharpen my blades I put about 6 pumps of grease in the spindles. I usually sharpen my BX2200 blades about two to three times year.

Bill

pro_tel · Mar 22, 2005

I you haven't found out yet, a 1 3/16 socket fits the bolt that secured the blades. I'm not certain what metric size that converts to.

tomnky · Mar 22, 2005

I use a 30mm six point socket to remove the blades on My mmm, this of course is on a BX2200

DanR67 · Mar 22, 2005

( Sorry for the ignorance here, but this is the 1st time I've had the bottom of the deck exposed. While I had the blades off, I pulled off the cap [dust cap?]. There was a little grease inside each cap. Should there have been more? I greased all the fittings when I 1st removed the deck back in December. Gotta say, I found some zerks that I did not know existed.
)

TDog -

In regards to greasing the MMM - there was a very interesting (and L-O-N-G /forums/images/graemlins/grin.gif) discussion about this late last spring. Grab a couple of your fav-o-rite beverages and check out this thread. Pictures and experiences galore - seems like some of the "Bota spindles were not exactly full of grease when they shipped. I'm happy to report that I've had no problems - but I'm glad I read that thread - one of my spindles took @ 20 pumps to fill! /forums/images/graemlins/shocked.gif

I've also taken the blade sharpening one-step farther: I bought another set of three and swap them all out at once. Then I can sharpen the set I removed *at my leisure*. Also some *quick-change* insurance in case I - or my lovely wife -takes to "granite mowing" any one of the rocks that stick up through the sod. I'm working on getting them out though! /forums/images/graemlins/grin.gif

*****************

BTW - I did the metric conversion: 1 3/16" = 30.something mm - so that is *close 'nuff*. To be exact - take your inch measurement as a decimal (1 3/16' = 1.1875) and multiply by 25.4 (1" = 25.4 mm)

Personally - I went out to Sears and bought a whole set of metric combination wrenches and 1/2" drive sockets - I think I've now got every size for my 'Bota - probably set me back @ $150. I figure something will eventually loosen up / wear out / break altogether etc - and then I'll be p!ssed that I don't have a wrench that fits. Dealers / hardware stores etc. are all at least 20 minute drive each way - so it's just some more *time insurance* I guess.

Cheers,

Dan

Tdog · Mar 22, 2005

Thanks to all for your patience - - and thanks Dan for pointing out that thread. Pretty scary. Guess I'll pull the blades again tomorrow & haul out the grease gun. There was a smidgen of grease around the inside edge of the dust caps, but not much.

Jack